Tom Brady runs for a first down in the second quarter. (Jim Rogash/Getty Images)

Updated with Bill Belichick comment

Hours after the New England Patriots advanced to Super Bowl XLIX, the NFL was looking into allegations that the team used deflated footballs in the AFC championship game against the Indianapolis Colts.

One ball, Bob Kravitz of WTHR.com and NBC’s WTHR-TV in Indianapolis reports, was taken out of action to be weighed and the NFL confirmed that it was looking into the matter that some are already calling #DeflateGate on Twitter. In his Monday afternoon press conference, Coach Bill Belichick said he first learned of the matter Monday morning and promised “we’ll cooperate fully with whatever the league wants, whatever questions they ask us.”

Related: Tom Brady calls accusation “ridiculous”

The NFL rule book states that game balls must be inflated with 12.5-13.5 pounds of air. Both teams at each game must provide a dozen balls each to be tested and approved 135 minutes before game time. The home team must also have 12 reserve balls available for testing, with the road team also having that option in outdoor games. The referee, the rules state, “shall be the sole judge as to whether all balls offered for play comply with these specifications. A pump is to be furnished by the home club, and the balls shall remain under the supervision of the referee until they are delivered to the ball attendant just prior to the start of the game.”

An underinflated or deflated ball would be easier to grip, which would have been advantageous in the pouring rain Sunday night. Tom Brady completed 23 of 35 passes for 226 yards and three touchdowns, with one interception, in the Patriots’ 45-7 crushing of the Colts and LeGarrette Blount had 30 carries for 148 yards and three touchdowns.

If the NFL determines that the balls were deliberately deflated — and proving intent is the key — punishment might involve the loss of draft picks and/or fines. The outcome of the game, obviously, would not be affected. As everyone knows, the Patriots have been here before. They were stripped of their 2008 first-round pick after the league determined they had videotaped signals used by opposing coaches in SpyGate. Bill Belichick was fined $500,000 and the team $250,000.

Belichick, on Sunday night, told fans, “It’s on to Seattle,” but it looks as if it won’t be that simple.